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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 91 · 40 sums
TalentJR

The method (Inside 180, outside the sum): Angle sum: ∠A + ∠B + ∠C = 180°. Exterior angle = sum of the two interior opposite angles. Right-angled triangle: longest side² = side² + side² (3, 4, 5 and 5, 12, 13 are famous sets). Sides can make a triangle only if the two shorter sides add up to more than the longest side.

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  1. 1.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  2. 2.In triangle ABC, angle A = 22° and angle B = 29°. What is angle C (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 57° and 22°. What is the exterior angle (in degrees)?
  4. 4.In triangle ABC, angle A = 83° and angle B = 48°. What is angle C (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  7. 7.In triangle ABC, angle A = 91° and angle B = 57°. What is angle C (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 59° and 41°. What is the exterior angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  10. 10.In triangle ABC, angle A = 59° and angle B = 20°. What is angle C (in degrees)?
  11. 11.In an isosceles triangle, the angle between the two equal sides is 94°. What is each of the other two angles (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 66°. What is each of the other two angles (in degrees)?
  13. 13.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  14. 14.The two interior opposite angles of a triangle are 67° and 34°. What is the exterior angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  16. 16.The two interior opposite angles of a triangle are 38° and 54°. What is the exterior angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  18. 18.In triangle ABC, angle A = 48° and angle B = 74°. What is angle C (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  20. 20.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  21. 21.The two interior opposite angles of a triangle are 73° and 20°. What is the exterior angle (in degrees)?
  22. 22.Can a triangle have sides of 21 cm, 12 cm and 4 cm? (a) No (b) Yes
  23. 23.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  24. 24.In an isosceles triangle, the two equal angles are 37° each. What is the third angle (in degrees)?
  25. 25.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  27. 27.An exterior angle of a triangle is 156°. One of its two interior opposite angles is 80°. What is the other one (in degrees)?
  28. 28.In triangle ABC, angle A = 64° and angle B = 29°. What is angle C (in degrees)?
  29. 29.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  30. 30.Can a triangle have sides of 5 cm, 6 cm and 5 cm? (a) No (b) Yes
  31. 31.Can a triangle have sides of 8 cm, 6 cm and 3 cm? (a) No (b) Yes
  32. 32.In an isosceles triangle, the angle between the two equal sides is 20°. What is each of the other two angles (in degrees)?
  33. 33.In triangle ABC, angle A = 73° and angle B = 59°. What is angle C (in degrees)?
  34. 34.Can a triangle have sides of 10 cm, 7 cm and 18 cm? (a) Yes (b) No
  35. 35.In triangle ABC, angle A = 21° and angle B = 94°. What is angle C (in degrees)?
  36. 36.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  37. 37.An exterior angle of a triangle is 115°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  38. 38.In triangle ABC, angle A = 67° and angle B = 22°. What is angle C (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  40. 40.In triangle ABC, angle A = 58° and angle B = 37°. What is angle C (in degrees)?

Answer key

  1. 40
  2. 129
  3. 79
  4. 49
  5. 61
  6. 23
  7. 32
  8. 100
  9. 51
  10. 101
  11. 43
  12. 57
  13. 24
  14. 101
  15. 90
  16. 92
  17. 36
  18. 58
  19. 138
  20. 5
  21. 93
  22. No
  23. 100
  24. 106
  25. 20
  26. 70
  27. 76
  28. 87
  29. 8
  30. Yes
  31. Yes
  32. 80
  33. 48
  34. No
  35. 65
  36. 90
  37. 79
  38. 91
  39. 47
  40. 85

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